1. Field of the Invention
This invention relates to a downhole connector, and in particular to an arrangement for ensuring the integrity of a sand screen or other filter medium at a connection between two lengths of expandable tubing utilized to support or form a sand screen or filter.
2. Description of the Related Art
In many well bores where a liquid, for example oil, passes from a surrounding formation into the well bore, the liquid will often carry entrained sand particles. If this sand is permitted to pass into the well bore, a number of problems may arise, including an increased likelihood of the well bore becoming blocked or restricted, and the sand may cause downhole tools to stick or jam, or wear prematurely. Accordingly, it is preferred that the sand particles are retained in the formation. This is achieved by providing screens or a filter around the casing or production tubing.
International Patent Application WO 97/17524 (Shell), the disclosure of which is incorporated herein by reference, describes a radially expandable assembly in which overlapping filter sheets are sandwiched between an inner expandable support tubing and an outer expandable protective tubing, the expandable tubing featuring large numbers of overlapping longitudinal slots. When an expander cone is forced through the assembly, the inner and outer tubing is expanded radially, the slots extending to form diamond-shaped openings. The initial degree of overlap between the screens is selected such that, although the screens move circumferentially relative to one another during expansion, the edges of the screens remain in overlapping relation. Such an arrangement can easily be constructed over sections of plain tubing or pipe. However, at the connections between tubing sections, where the inner tubing sections are coupled together, it is difficult to maintain a “sand-tight” joint.
It is among the objectives of embodiments of the present invention to provide a connector arrangement which obviates or mitigates this difficulty.